Camera system

ABSTRACT

According to this invention, a camera system has a camera body and a first and second lenses exchangeable to the camera body. The first lens comprises a device for outputting first data which indicates the first lens belongs to a first lens type. The second lens comprises a device for outputting second data which indicates the second lens belongs to a second lens type and third data with respect to the characteristic of the second lens. The camera body comprises: a device for inputting the data from the outputting device of the first or second lens attached to the camera body, a device for discriminating the lens type based on whether the inputted data is the first or second data, a device for storing data with respect to the characteristic of the lens belonging to the first lens type, and a processing device for carrying out a process based on the third data when the discriminating device judges the attached lens belongs to the second lens type and controlling it based on the stored data in the storing device when the discriminating device judges the attached lens belongs to the first lens type. The discriminating means judges the attached lens belongs to the first lens type.

This application is a divisional of application Ser. No. 07/315,845,filed Feb. 27, 1989, now U.S. Pat. No. 5,003,336.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a camera system comprising anexchangeable lens having individual information of its own to beoutputted to a camera body and the camera body which performs variousoperations using the information inputted thereto from the exchangeablelens. The present invention further relates to a camera system having aplurality of focus detection areas.

2. Description of the Prior Art

Individual information of lenses to be required to be controlled by acamera body increases as a camera system has more functions such as anautomatic focusing control. Heretofore, information such as a fully openaperture value is mechanically transmitted from a lens to the camerabody. Therefore, the number of kinds of information is small and theinformation cannot be transmitted from the lens to the camera body witha high accuracy. In order to overcome this problem, various camerasystems are proposed. According to a known camera system, a read onlymemory (ROM) which stores the individual data of respective lenses ismounted in the lens so as to electrically transmit the lens data fromthe lens to the camera body.

The specification of German Patent No. 3518887 discloses a camera systemin which a storing means provided in each of the lenses stores anelectric signal peculiar to each of the lenses while the camera bodystores the lens data on these lenses. According to this camera system,the lens data stored in the camera body is selected in response to anelectric signal transmitted from the lens, whereby an exposure controlappropriate to the lens can be made.

But as the camera system is provided with more and more functions suchas a focus condition detection in a plurality of focus detection areas,i.e., when lens data to be controlled by the camera body increasesfurther, the following problem occurs in the above-described cameras: ifa conventional lens which includes the ROM which stores the lens datanecessary only for the function of the conventional camera, is mountedon a developed camera body, the camera body can not operate thedeveloped function operate thereof due to the shortage of lens data eventhough the mounting portion of the lens barrel can be attached to themounting portion of the camera body.

The provision of a storing means in the camera body which stores theindividual lens data of respective lenses does not allow the occurrenceof such a problem, but the storing means is required to store a largeamount of data therein, which is not preferable in view of practicaluse.

Next, lens data necessary for detecting a focus condition is considered.Heretofore, even if an object is sufficiently bright and has a highcontrast, in some cases, a focus detecting operation must be controlleddepending on the configuration and condition of a lens in a camera whichhas a single focus detection area and performs only the focus conditiondetection of an object present in an area including an optical axis.Such a control must be made in the following cases: The condition to bedetermined by diameter and position of the exit pupil of the lens suchas a reflecting telephoto lens is not suitable for a focus detectingelement; the light reflected from an object is not incident on an entirefocus detecting element because the diameter of the exit pupil of a lensis too small (a vignetting occurs in this case); and amacro-photographing in which the position of the diameter of the exitpupil changes, the depth of focus becomes shallow, and the aperturevalue becomes great.

The specification of U.S. Pat. No. 4,509,842 discloses the followingart. A signal, indicating that it is impossible to detect a focuscondition, is stored in a storing means provided in a lens such as areflecting telephoto lens. It is decided whether or not a fully openaperture value stored in the lens as lens data exceeds a predeterminedvalue (for example, F=5.6). And a signal, indicating that a focuscondition cannot be detected, is outputted from the lens when the lensis used to carry out a macro-photographing.

However, the above-described arts all relate to the camera system whichhas a single focus detection area and detects only the focus conditionof an object present in an area including an optical axis, i.e., thesearts cannot be applied to a camera system having a plurality of focusdetection areas in a photographing picture plane. That is, the knowncamera system is provided with only data which indicates whether or notit is possible to detect a focus condition on an axial focus detectionarea. Contrary to such a camera system, in the camera system in which aplurality of focus detection areas are provided in the photo-takingpicture plane, a focus detection area which can be used, is variedaccording to the condition determined by the configuration of the exitpupil of the lens and the diameter as well as the position of the exitpupil thereof. Therefore, it is necessary to store as lens data theinformation of respective lenses in the storing means provided in thelens, which indicates which of a plurality of focus detection areas canbe used.

When the conventional lens used in the camera system having a singlefocus detection area is used in a camera system having a plurality offocus detection areas, as described above, the problem that the lensdata is short occurs.

It is preferable that a focus condition is detected by using a greatarea in order to detect a focus condition with a high accuracy, but avignetting occurs when a lens whose exit pupil is small (for example, atelephoto lens whose focal length is too long) is used although there isno problem with a lens whose exit pupil is great. In this case, a focuscondition cannot be detected. In order to detect a focus condition notonly for a lens whose exit pupil is great, but also for a lens whoseexit pupil is small, it is necessary to prevent the occurrence of avignetting. To this end, it is necessary to reduce a focus detectionarea, which means that a focus condition cannot be detected with a highaccuracy.

That is, the known camera has a problem that the improved accuracy of afocus condition detection is inconsistent with the increase of thenumber of the kinds of lens which can be used for detecting a focuscondition.

The above-described camera system has another problem which is describedhereinbelow.

As described previously, in this kind of camera, various kinds ofexchangeable lenses are used as a photo-taking lens. A photo-taking lensis composed of only a lens or of a lens and a converter lens forconverting the focal length of the photo-taking lens.

The converter lens for use in this kind of camera transfers the lensdata transmitted from the lens directly to the camera body in order toenable a focus detecting operation and converts the lens data, which isvaried by the converter lens, such as the focal length or the fully openaperture value at the same rate of change as that of the focal length,thus outputting the converted data to the camera body.

Furthermore, according to the known camera body, whether or not avignetting occurs is detected based on the fully open aperture valueobtained from the lens. In this respect, it may be considered whether ornot a focus condition can be detected by using the fully open aperturevalue converted by the converter lens when the lens is used with theconverter lens mounted thereon as well.

But the position of the exit pupil of the lens attached to the converterlens may change along the optical axis to a greater extent than theposition of the exit pupil of the lens not attached to the converterlens. In this case, it cannot be accurately decided whether or not afocus condition can be detected according to the information of thefully open aperture value which is converted at the same rate of changeas that of the focal length due to the operation of the converter lens.

That is, in the known camera system, even though a vignetting does notoccur due to the change of the position of the exit pupil, it is decidedthat the vignetting will occur only according to the information of thefully open aperture value, so that it can be decided that the focuscondition can not be detected. In particular, in a camera system havinga plurality of focus detection areas, a focus detection area which canbe used for detecting a focus condition is changed greatly by the changeof the position the exit pupil, thus causing the above problem.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a camera systemcapable of achieving a novel function using a photo-taking lensbelonging to the category of the known camera system when the camerabody thereof is provided with the novel function not provided with theknown camera system.

It is another object of the present invention to provide a camera systemcapable of determining which of a plurality of focus detection areas canbe used depending on each lens.

It is still another object of the present invention to provide a camerasystem which can increase the number of kinds of lenses capable ofdetecting a focus condition and selecting focus detection areas suitablefor the respective lenses.

It is a further object of the present invention to provide a camerasystem capable of appropriately deciding which of a plurality of focusdetection areas can be used when a converter lens is used.

It is a still further object of the present invention to provide acamera system having a storing means, provided in a lens, for storinginformation for performing various functions.

In accomplishing these and other objects, there is provided a camerasystem having a camera body and a first and second lenses exchangeableto said camera body, comprising: said first lens comprising means foroutputting first data which indicates said first lens belongs to a firstlens type; said second lens comprising means for outputting second datawhich indicates said second lens belongs to a second lens type and thirddata with respect to the characteristic of said second lens, said camerabody comprising: means for inputting the data from the outputting meansof said first or second lens attached to said camera body, means fordiscriminating the lens type based on whether the inputted data is thefirst or second data, means for storing data with respect to thecharacteristic of said lens belonging to the first lens type, and aprocessing means for carrying out a process based on the third data whenthe discriminating means judges the attached lens belongs to the secondlens type and controlling it based on the stored data in the storingmeans when the discriminating means judges the attached lens belongs tothe first lens type.

In another aspect of the present invention, there is provided a camerasystem having a camera body and a first and second lenses exchangeableto said camera body, comprising: said first lens comprising means foroutputting first data which indicates said first lens belongs to a firstlens type; said second lens comprising means for outputting second datawhich indicates said second lens belongs to a second lens type and thirddata with respect to the characteristic of said second lens, said camerabody comprising: means for inputting the data from the outputting meansof said first or second lens attached to said camera body, a firststoring means, a second storing means, a third storing means for storingdata with respect to the characteristic to said lens belonging to thefirst lens type, means for making the inputted first and second datastore in the first storing means, means for discriminating the lens typebased on whether the stored data is the first or second data, and meansfor making the inputted third data store in the second storing meanswhen the discriminating means judges the attached lens belongs to thesecond lens type and making the stored data in the third storing meansstore data in the second storing means when the discriminating meansjudges the attached lens belongs to the first lens type.

In a further aspect of the present invention, there is provided a camerasystem detectable focus conditions on a plurality of focus detectionareas having a camera body and an exchangeable lens to said camera body,comprising: said lens comprising means for outputting data whichindicates which of the focus detection area is able to be used in thefocus detection and irrespective of an exit pupil; said camera bodycomprising means for inputting the data from the outputting means ofsaid attached lens to the camera body, means for selecting the focusdetection area based on the inputted data, and means for detecting thefocus condition on the focus detection area selected by the selectingmeans.

In a further aspect of the present invention, there is provided a lensexchangeable to a camera body which can detect focus conditions on aplurality of focus detection areas, comprising means for outputting datawhich indicates which of the focus detection areas is able to be used inthe focus detection.

In a further aspect of the present invention, there is provided a camerabody inputted data from a lens, the data indicates an aperture value forfocus detection, comprising: a first means for detecting a focuscondition with respect to a first focus detection portion; a secondmeans for detecting a focus condition with respect to a second focusdetection portion; means for comparing the inputted data with apredetermined value; and means for selecting one of the first and secondfocus detecting means based on a resultant of the comparing means.

In a further aspect of the present invention, there is provided a camerasystem having a camera body, an exchangeable lens to said camera bodyand a converter lens exchangeable between said camera body and saidexchangeable lens, comprising; said exchangeable lens comprising meansfor outputting first data indicative of an aperture value for focusdetection and second data; said converter lens comprising means forinputting the data outputted from the outputting means of saidexchangeable lens attached to said converter lens, means for convertingthe inputted first data into third data, and means for outputting thethird data and the second data inputted from the outputted means of saidexchangeable lens to the inputting means; said camera body comprisingmeans for inputting the second and third data from said converter lensattached to said camera body, a first means for detecting a focuscondition with respect to a first focus detection portion, second meansfor detecting a focus condition with respect to a second focus detectionportion, means for comparing the inputted third data with apredetermined value, means for changing the predetermined value based onthe inputted second data, and means for selecting one of the first andsecond focus detecting means based on a resultant of the comparingmeans.

In a further aspect of the present invention, there is provided a camerasystem having a camera body, an exchangeable lens to said camera bodyand a converter lens exchangeable between said camera body and saidexchangeable lens, comprising: said exchangeable lens comprising meansfor outputting first data indicative of an aperture value for focusdetection and second data indicative of an admitting degree with respectto a portion of an exit pupil of said exchangeable lens; said converterlens comprising means for inputting the data from the outputting meansof said exchangeable lens attached to said converter lens, means forconverting the inputted first data into third data, and means foroutputting the second and third data; said camera body comprising meansfor inputting the second and third data from said converter lensattached to said camera body, a first means for detecting a focuscondition with respect to a first focus detection portion, a secondmeans for detecting a focus condition with respect to a second focusdetection portion, and means for selecting one of the first and secondfocus detecting means based on second and third data.

In a further aspect of the present invention, there is provided a lensexchangeable to a camera body which can detect focus conditions on aplurality of focus detection areas, comprising means for outputtingfirst data indicative of an aperture value for focus detection andsecond data indicative of an admitting degree with respect to a positionof an exit pupil of said lens.

By the arrangement according to the present invention, since stored inthe camera body is the data (e.g. new data) with respect to thecharacteristic of said first lens (e.g. conventional lens), even if thefirst lens has no data which is necessary for performing new developedfunction, the new developed function can be performed. On the otherhand, when the discriminating means judges the attached lens is thesecond lens type, new function can be performed based on the third datain which the second lens has. Only the data necessary for performing thenew function at the first lens type is stored in the camera body.Therefore, it is unnecessary to store a great many data in the camerabody.

Moreover, by the arrangement according to the present invention, sincethe camera system capable of determining which of a plurality of focusdetection areas can be used depending on a lens, a focus detectingperformance is improved and various photo-taking lens can be used.Further, a focus condition can be detected in an appropriate conditiondepending on the kind of a photo-taking lens. Furthermore, the camerasystem can increase the number of kinds of lenses capable of detecting afocus condition. Moreover, the camera system can appropriately decidewhich of a plurality of focus detection areas can be used when aconverter lens is used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a camera system according to oneembodiment of the present invention;

FIG. 2-(a) is a circuit diagram of a camera body of the system;

FIG. 2-(b) is a partial view of the circuit;

FIG. 3 is a perspective view showing the periphery of a focus detectingoptical system in the system;

FIG. 4 is a field view in a finder in the system;

FIG. 5 is an enlarged front view of a light receiving unit of a CCD linesensor in the system;

FIG. 6-(a) through 6-(d) are schematic diagram showing the relationshipbetween the exit pupil of a phototaking lens and the entrance pupil ofthe focus detecting optical system;

FIG. 7 through FIG. 11 are flowcharts showing the operation of thecamera system;

FIG. 12 is an explanatory view showing the relationship between a focusdetecting aperture value and a focus detection area; and

FIGS. 13 and 14 are flowcharts showing another embodiments of theoperations of the camera system, respectively.

FIG. 15 is a block diagram showing an entire circuit of a camera systemaccording to another embodiment of the present invention;

FIG. 16-(a) through 16-(e) are schematic diagram showing therelationship between the exit pupil of a photo-taking lens and theentrance pupil of the focus detecting optical system;

FIG. 17 is a view showing the relationship between an in-focus positioncaused by an AF sensor and the best focal plane position based on theaberration of a photo-taking lens;

FIG. 18 is a flowchart showing the main operation of the CPU in thesystem;

FIG. 19 is a flowchart showing a subroutine for reading ROM data;

FIG. 20 is a flowchart showing a subroutine for reading the ROM datainto a RAM provided in the camera body;

FIG. 21 is a flowchart showing a subroutine for the processing of aserial interruption into the CPU;

FIG. 22 is a flowchart showing a subroutine for referencing the datatable provided in the camera body;

FIG. 23 is a flowchart showing a subroutine for detecting an automaticfocus condition;

FIGS. 24a and 24b are flowcharts showing a subroutine for calculating afocus condition detection;

FIG. 25 is a flowchart showing an embodiment of a subroutine for adefocus amount calculation under a visible light;

FIG. 26 is a flowchart showing an embodiment of a subroutine for adefocus amount calculation using a complementary light;

FIG. 27 is a flowchart showing another embodiment of a subroutine for adefocus amount calculation under a visible light;

FIG. 28 is a flowchart showing another embodiment of a subroutine for adefocus amount calculation using a complementary light;

FIG. 29 is a flowchart showing a subroutine for calculating a lenscontrolling defocus amount;

FIGS. 30a and 30b shows an area map of the ROM provided in the lens; and

FIG. 31 shows an area map of the data table provided in the camera body.

DETAILED DESCRIPTION OF THE INVENTION

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numerals andsymbols throughout the accompanying drawings.

Referring to FIG. 2-(a) showing the circuit diagram of a camera body ofa camera system in accordance with one preferred embodiment of thepresent invention, a circuit 1 provided in the camera body and a circuit5 provided in a converter lens are electrically connected to each otherby a group of contacts 711 through 715 mounted on the camera body and agroup of contacts 721 through 725 mounted on the converter lens. Thecontacts 711 through 715 and 721 through 725 are provided on a mountportion 7.

The circuit 5 in the converter lens and a circuit 6 provided in aphoto-taking lens are electrically connected to each other by a group ofcontacts 811 through 815 mounted on the converter lens and a group ofcontacts 821 through 825 mounted on the photo-taking lens. The contacts811 through 815 and 821 through 825 are provided on a mount portion 8.

All circuits which are described later are operated by the instructionof a central processing unit 100 (hereinafter referred to as CPU) whichcontrols the operation of the entire system. A constant voltage Vcc issupplied by a power source 10 to the CPU 100, the circuit 5 in theconverter lens, and the circuit 6 in the photo-taking lens.

A light measuring circuit 310 performs an A/D conversion of aphotoelectrically converted amount (corresponding to the luminance valueof an object to be photographed) of a light measured by a lightmeasuring element (not shown) which performs a TTL light measuring.Thus, the light measuring circuit 310 outputs to the CPU 100 theluminance value data BV₀ (BV₀ =BV-AV₀ : AV₀ is fully open aperture valueof the photo-taking lens) of the object which is calculated by APEXsystem.

An exposure control circuit 320 controls the operation of the diaphragmmechanism (not shown) of the photo-taking lens and the shutter mechanism(not shown) of the camera body based on the instruction of the CPU 100.

An automatic focus adjusting circuit 330 comprises a focus detectingcircuit (not shown) and a control circuit (not shown) for driving thelens.

A display circuit 340 displays photographing information such as theexposure mode and exposure control values (aperture value and shutterspeed) of the camera, the number of frames of a film exposed, and thefocus condition (in-focus or out of focus) of the photo-taking lens.

A complementary light circuit 350 projects a complementary light on theobject when it is impossible to detect a focus condition of the objectunder a visible light. The construction of the complementary circuit 350is disclosed in Japanese Patent Application No. 62-141538, and theapplication of which was filed by the present applicant.

A film sensitivity information circuit 360 transfers the filmsensitivity information of a film to the CPU 100 based on a DX code readout from the patrone put in the camera body.

An oscillation circuit 370 supplies a pulse signal to be used as anoperation clock to the CPU 100 while various operations are beingperformed.

A light measuring switch 112 SW1 is closed during the depression of ashutter release button (not shown) through a first half of its fullstroke. A release switch 114 SW2 is closed when the shutter releasebutton is completely depressed through the full stroke.

The mount portions 7 and 8 are described hereinbelow. The mount portion7 provided between the camera body and the converter lens comprises amount 71 provided on the camera body on which the photo-taking lens ismounted and a mount 72 provided on the converter lens. The mount 8provided between the converter lens and the photo-taking lens comprisesa mount 81 provided on the converter lens and a mount 82 on thephoto-taking lens. In the camera of the embodiment, the mounts 71 and 72of the mount portion 7 comprise five contacts 711 through 715 and 721through 725, respectively, and the mounts 81 and 82 of the mount portion8 comprise five contacts 811 through 815 and 821 through 825,respectively. The circuit connection as described below allows a serialcommunication between the CPU 100 in the circuit 1 provided in thecamera body and the circuit 6 provided in the photo-taking lens throughthe circuit 5 provided in the converter lens.

The CPU 100 provided in the camera body comprises an output terminal 102Sck for outputting a clock signal to be used for a serial input/output,an input terminal 103 Sin for serially reading the data inputted theretofrom the circuit 6 provided in the photo-taking lens, and an outputterminal 104 CS for outputting a signal which commands the drive timingof the circuit 6 provided in the photo-taking lens. The contacts 712,713, and 714 of the mount 71 on the camera body are connected to theclock output terminal 102, the input terminal 103, and the outputterminal 104, respectively. The contact 711 is connected to the powersource 10 through a resistor 14 for preventing the occurrence of ashort-circuit. The contact 715 is connected to the earth line of thecircuit 1 in the camera body.

In the converter lens, of the group of five contacts 721 through 725 ofthe mount 72 connected to the mount 71 on the camera body and the groupof five contacts 811 through 815 of the mount 81 connected to the mount82 on the photo-taking lens, the contact 721 is connected to the contact811 and to a power source terminal 501 of the circuit 5 in the converterlens, the contact 725 is connected to the contact 815 and to an earthterminal 505 of the circuit 5 in the converter lens, the contact 723 isconnected to the contact 813 through a conversion circuit 555 of thecircuit 5 in the converter lens, and the contacts 722 and 724 areconnected to the contact 812 and 814, respectively.

In the photo-taking lens, of the group of the five contacts 821 through825 of the mount 82 provided on the photo-taking lens, the contact 821is connected to a power source terminal 601 of the circuit 6 in thephoto-taking lens, the contact 825 is connected to an earth terminal ofthe circuit 6 in the photo-taking lens, and the contacts 822 through 824are connected to a parallel/serial conversion circuit 65 of the circuit6 in the photo-taking lens.

A ROM 64 of the circuit 6 provided in the photo-taking lens previouslystores individual information on the photo-taking lenses. When the PSconversion circuit 65 receives a signal, outputted from clock outputterminal 102 of the CPU 100, indicative of the transfer of the lensinformation, the lens information are read out from the ROM 64 to PSconversion circuit 65 in parallel. The lens information is shown inTable 1 according to the addresses in which the respective lensinformation is stored.

                  TABLE 1                                                         ______________________________________                                        Address                                                                              Data                    Symbol                                         ______________________________________                                        01     Lens Mounting Signal    ICP                                            02     Fully Open Aperture Value                                                                             AV.sub.0                                       03     Minimum Aperture Value  AV.sub.max                                     04     Variation Amount Data   ΔAV                                             of Aperture Value due to Zooming                                       05     Focal Length            f                                              06     Conversion Coefficient for Finding Drive                                                              K                                                     Amount according to Defocus Amount                                     07     AF Aperture Value       AFAV.sub.0                                     08     Off-axial Focus Detection Signal                                                                      OFF.sub.ok                                     09     Axial Focus Detection Signal                                                                          FAEN.sub.2                                     0A     Off-axial Focus Admitting Signal                                                                      WB                                             0B     AF Lens Deciding Signal AFC                                            0C     Converter Lens Mounting Signal                                                                        CNVSET                                         ______________________________________                                    

The PS conversion circuit 65 of the circuit 6 in the photo-taking lensconverts the parallel signal applied from the ROM 64 into serialsignals, thus outputting the serial signals to the circuit 5 in theconverter lens through the contacts 823 and 813.

Of the information inputted to the conversion circuit 555 of the circuit5 in the converter lens, the conversion circuit 555 converts the lensinformation, for example, an aperture value which is modified by themounting of the converter lens. The conversion circuit 555 outputs otherlens information as they are to the input terminal 103 of the CPU 100through the contacts 723 and 713. The conversion circuit 555 alsoconverts the data of a focal length etc. in addition to the aperturevalue.

FIG. 2-(b) shows in detail the three input/output terminals 102, 103,and 104 provided in the CPU 100 shown in FIG. 2-(a).

A high enable circuit is connected to the output terminal 102 and whilea serial port control register SCKC is at a high level, a clock pulse isoutputted from the camera body to the photo-taking lens through theoutput terminal 102. The serial counter 120 is a 3-bit counter forcounting the clock pulse of 1 byte (eight pulses). When the serialcounter 120 has counted the clock pulse of 1 byte (eight pulses), theserial counter 120 outputs an interruption signal INT to the CPU 100.

A serial register 121 connected to the input terminal 103 temporarilystores data transferred by one bit according to the clock pulse from thephoto-taking lens. The 8-bit data of the particular address of the ROM64 stored in the serial register 121 is stored in the random accessmemory (hereinafter referred to as RAM) (not shown) provided in thecamera body according to the interruption signal produced from theserial counter 120.

Next, the outline of the construction of the focus condition detectingdevice to be applied to the present invention is described hereinbelow.

Referring to FIG. 3, lenses TL₁ and TL₂ constituting the photo-takinglens TL are spaced, from a focal plane FP on which an image is to beformed. A field mask FM is provided in the vicinity of the focal planeFP. The field mask FM is provided with a horizontally elongated firstrectangular opening E₀ in the center portion thereof and verticallyelongated second and third rectangular openings E₀₁ and E₀₂ on bothsides of the first rectangular opening E₀. A light flux which has beenreflected by the object and passed through the rectangular openings E₀,E₀₁, and E₀₂ passes through condenser lenses L₀, L₀₁, and L₀₂(hereinafter referred to as a first condenser lens L₀, a secondcondenser lens L₀₁, a third condenser lens L₀₂ in correspondence withthe rectangular openings E₀, E₀₁, and E₀₂ of the field mask FM), andthen, the respective light fluxes converge.

An aperture mask AM and an image re-forming lens plate L are disposedbackward of the condenser lenses L₀, L₀₁, and L₀₂. The image re-forminglens plate L is provided with a pair of image re-forming lenses L₁ andL₂ horizontally arranged in the center portion thereof, a pair of imagere-forming lenses L₃ and L₄ and a pair of image re-forming lenses L₅ andL₆, respectively, vertically arranged on both sides of the imagere-forming lenses L₁ and L₂. These image re-forming lenses L₁ through L₆consist of flat convex lenses having the same radius of curvature (thepair of image re-forming lenses L₁ and L₂ arranged in the centerportion, the pair of image re-forming lenses L₃ and L₄ and the pair ofimage re-forming lenses L₅ and L₆ arranged on both sides of the imagere-forming lenses L₁ and L₂ are hereinafter referred to as a first pairof image re-forming lenses, a second pair of image re-forming lenses, athird pair of image re-forming lenses in correspondence with therectangular openings E₀, E₀₁, and E₀₂ of the field mask FM).

The aperture mask AM is provided with aperture openings A₁ through A₆corresponding to the positions of the image re-forming lenses L₁ throughL₆. The aperture mask AM is arranged immediately forward of the imagere-forming lens plate L and in close contact with the flat portions ofthe image re-forming lens plate L.

A substrate P provided with three CCD line sensors P₀, P₀₁, and P₀₂ isarranged backward of the image reforming lens plate L. The CCD linesensor P₀ arranged in the center portion of the substrate P ishorizontally elongated and the CCD line sensors P₀₁ and P₀₂ arranged onboth sides of the CCD line sensor P₀ are vertically elongated so thatthe arrangement directions of the respective pair of the imagere-forming lenses provided on the image reforming lens plate Lcorrespond to the arrangement directions of the CCD line sensors P₀,P₀₁, and P₀₂. The CCD line sensors P₀, P₀₁, and P₀₂ are provided withfirst and second light receiving elements arranged in a row,respectively. The light receiving elements separately photoelectricallyconvert two images re-formed on the CCD line sensors by the pair of theimage re-forming lenses (the CCD line sensors P₀, P₀₁, and P₀₂ arehereinafter referred to as a first CCD line sensor P₀, a second CCD linesensor P₀₁, and a third CCD line sensor P₀₂ in correspondence to therectangular openings E₀, E₀₁, and E₀₂ of the field mask FM).

The members in a block AFMO enclosed by dotted lines in FIG. 3 is heldtogether as a unit, thus constituting an AF sensor module. A focusdetecting optical system is composed by the field mask FM, the condenserlenses L₀, L₀₁, and L₀₂, the aperture mask AM, and the image re-forminglens plate L.

The focus detecting device detects a focal point as follows using animage obtained by the focus detecting optical system having theabove-described construction.

A light flux out of the optical axis O_(p) for detecting a focuscondition (hereinafter referred to as off-axial focus detection lightflux), including principal rays l₃ and l₄ reflected by the object whichis located on the area out of the optical axis O_(p) of the photo-takinglens TL, are incident on the field mask FM such that the off-axial focusdetection light flux are distant from the optical axis O_(p) at apredetermined angle, pass through the second rectangular opening E₀₁,and are incident on the second condenser lens L₀₁. The off-axial focusdetection light flux is bent toward the optical axis O_(p) and convergedby the second condenser lens L₀₁ and incident on the second pair ofimage re-forming lenses L₃ and L₄ of the image re-forming lens plate Lthrough the second aperture openings A₃ and A₄ of the aperture mask AM.The off-axial focus detection light flux which is incident on the secondpair of image re-forming lenses L₃ and L₄ is converged on the second CCDline sensor P₀₁ by the second pair of image re-forming lenses L₃ and L₄.As a result, a pair of images is vertically re-formed on the second linesensor P₀₁.

Similarly, an off-axial focus detection light flux including theprincipal rays l₅ and l₆ are incident on the field mask FM such that itbecomes distant from the optical axis O_(p) at a predetermined angle andis converged on the third CCD line sensor P₀₂ through the thirdrectangular opening E₀₂, the third condenser lens L₀₂, the thirdaperture openings A₅ and A₆ of the aperture mask AM, and the third pairof the image re-forming lenses L₅ and L₆, with the result that a pair ofimages are vertically re-formed on the third CCD line sensor P₀₂.

A bundle of rays on the optical axis for detecting a focus condition(hereinafter referred to as axial focus detection light flux), includingthe principal rays l₁ and l₂ which are reflected by the object which isdisposed in the area including the optical axis O_(p) of thephoto-taking lens TL, is converged on the first CCD line sensor P₀through the first rectangular opening E₀ on the optical axis O_(p) ofthe field mask FM, the first condenser lens L₀, the first apertureopenings A₁ and A₂ on the optical axis O_(p) of the aperture mask AM,and the first pair of the image re-forming lenses L₁ and L₂, with theresult that a pair of images is laterally re-formed on the first CCDline sensor P₀.

A focal point of the photo-taking lens TL which is focused on the objectcan be detected by obtaining the positions of three pairs of imagesre-formed on the CCD line sensors P₀, P₀₁, and P₀₂.

Referring to FIG. 4 in which the field in the finder is shown, the firstCCD line sensor P₀, the second CCD line sensor P₀₁, the third CCD linesensor P₀₂ correspond to the axial focus detection area FA, theoff-axial focus detection area FA₁ disposed on the right, and theoff-axial focus detection area FA₂ disposed on the left, respectively.It is possible to detect the focus condition of objects disposed in thethree focus detection areas FA, FA₁, and FA₂ (hereinafter referred to asa first island FA, a second island FA₁, and a third island FA₂ whenthese three areas are necessary to be distinguished from each other).

The focus detecting circuit of the automatic focus adjusting circuit 330performs a focus detection using the signals outputted from the CCD linesensors P₀, P₀₁, and P₀₂. The control circuit for driving the lensdrives the photo-taking lens TL toward an in-focus position based on theresult detected by the focus detecting circuit.

Referring to FIG. 3, six areas A₁₁, A₂₁, A₃₁, A₄₁, A₅₁, and A₆₁ shown bybroken lines on the photo-taking lens TL₁ and six areas A₁₂, A₂₂, A₃₂,A₄₂, A₅₂, and A₆₂ shown by broken lines on the photo-taking lens TL₂ areimages (hereinafter referred to as projected image) of the apertureopenings A₁, A₂, A₃, A₄, A₅, and A₆ of the aperture mask AM on thephoto-taking lenses TL₁ and TL₂ projected through the three condenserlenses L₀, L₀₁, and L₀₂. The areas A₁₁, A₂₁, A₃₁, A₄₁, A₅₁, and A₆₁ andA₁₂, A₂₂, A₃₂, A₄₂, A₅₂, and A₆₂ indicate the areas in which the focusdetection light fluxes, which pass through the six apertures A₁, A₂, A₃,A₄, A₅, and A₆, pass the two photo-taking lenses TL₁ and TL₂.Accordingly, if the six projected images A₁₁, A₂₁, A₃₁, A₄₁, A₅₁, andA₆₁ on the photo-taking lens TL₁ and the six projected images A₁₂, A₂₂,A₃₂, A₄₂, A₅₂, and A₆₂ on the photo-taking lens TL₂ are included in thepupils of the photo-taking lenses TL₁ and TL₂, the focus detection lightfluxes which are incident on the three CCD line sensors P₀, P₀₁, and P₀₂are not vignetted in the photo-taking lenses TL₁ and TL₂. Thus, theobject can be brought into focus with a high accuracy based on the focuscondition detection using the outputs of the three CCD line sensors P₀,P₀₁, and P₀₂.

FIG. 5 shows in detail the light receiving unit of the CCD line sensor(CCD line sensor includes a light receiving unit, a charge accumulatingunit (not shown), and a transfer unit (not shown)) to be used in thefocus detecting device. The line sensor P₀ is provided with a standardportion P_(0s) and a reference portion P_(0r). The line sensor P₀₁ isprovided with a standard portion P_(01s) and a reference portionP_(01r). The line sensor P₀₂ is provided with a standard portion P_(02s)and a reference portion P_(02r). There is provided a monitoring lightreceiving element MA for controlling an integration period for theaccumulating unit of the CCD line sensor on one side of the standardportion P_(0s) of the line sensor P₀. The number of picture elements ofthe standard portions P_(0s), P_(01s), and P_(02s) and the referenceportions P_(0r), P_(01r), and P_(02r) of the line sensors P₀, P₀₁, andP₀₂ is 44, 52 in the line sensor P₀ and 34, 44 in the line sensors P₀₁,and P₀₂. The CCD line sensors P₀, P₀₁, and P₀₂ are formed on one chip.

In the focus detecting device according to this embodiment, the standardportion P_(0s) of the line sensor P₀ is divided into a plurality ofblocks and each of the divided blocks of the standard portion P_(0s) iscompared with the entire reference portion P_(0r) so as to detect afocus condition. The line sensor P₀ is provided with an entire block Pawhich uses the picture elements in the entire area thereof and a partialblock Pb which uses only the picture elements disposed in the centerthereof. Specifically, 44 picture elements are used in the entire blockPa and 24 picture elements disposed in the center thereof are used inthe partial block Pb.

In detecting a focus condition, the following three focus adjustingmodes are available. According to a first mode, one of the three islandsFA, FA₁, and FA₂ is selected and a focus condition is adjusted based ona defocus amount obtained from the selected island (this mode ishereinafter referred to as multipoint focus detection mode). Accordingto a second mode, only the first island FA is used and a focusingcondition is adjusted based on the defocus amount obtained from theentire block Fa (this mode is hereinafter referred to as wide focusdetection mode). According to a third mode, only the partial block Fb ofthe first island FA is used to adjust a focus condition based on thedefocus amount obtained from the partial block Fb (this mode ishereinafter referred to as spot focus detection mode). These mode can beswitched to each other.

FIGS. 6-(a) through (d) show the images A₁₂, A₂₂, A₃₂, A₄₂, A₅₂, and A₆₂of the six aperture openings A₁, A₂, A₃, A₄, A₅, and A₆ of the aperturemask AM on the exit pupil of various kinds of photo-taking lensesprojected through the three condenser lenses L₀, L₀₁, and L₀₂.

FIG. 6-(a) shows a projected image on the exit pupil when a photo-takinglens TL_(a) whose pupil is great is used. Since the pupil is great, allof the projected images A₁₂, A₂₂, A₃₂, A₄₂, A₅₂, and A₆₂ exist on theexit pupil TL_(ao) of the photo-taking lens TL_(a) and all of lightfluxes, adapted for detecting a focus condition, which are incident onthe CCD line sensors P₀, P₀₁, and P₀₂ are not vignetted by the pupil ofthe photo-taking lens TL_(a), and as such, can be used for detecting afocus condition. That is, since the focus condition can be detected inall of the focus detection areas FA, FA₁, and FA₂, the multipoint focusdetection mode is selected.

FIGS. 6(b) through (d) show projected images on the exit pupil whenphoto-taking lenses whose pupils are smaller than the pupil of thephoto-taking lens shown in FIG. 6-(a) are used.

In the photo-taking lens TL_(b) shown in FIG. 6-(b) since the pupilTL_(b0) thereof is small, a light flux which is capable of beingincident on the CCD line sensor without being vignetted by the pupil ofthe photo-taking lens TL_(b) is only an axial focus detection lightflux. Therefore, the island which is capable of detecting a focuscondition is only the first island FA disposed in the center of thefield in the finder shown in FIG. 5. Accordingly, in this case, the widefocus detection mode which detects a focus condition using the entireblock Fa of the first island FA is selected.

In the photo-taking lens TL_(c) shown in FIG. 6-(c), since the pupilTL_(c0) thereof is smaller than the pupil TL_(b0) of the photo-takinglens TL_(b) shown in FIG. 6-(b), the light flux which is incident on thefirst island FA, namely, the axial focus detection light flux isvignetted. But the portion which is vignetted is part of the outerportion of the first island FA. Accordingly, in this case, the spotfocus detection mode in which a focus condition is detected by using thepartial block Fb of the first island FA is selected.

In the photo-taking lens TL_(d) shown in FIG. 6-(d), since the pupilTL_(d0) thereof is smaller than the pupil TL_(c0) of the photo-takinglens TL_(c) shown in FIG. 6-(c), most of the focus detection lightfluxes which are incident on the first island FA is vignetted, so that afocus condition cannot be detected. Accordingly, a focus condition isnot detected.

On receipt of lens data transferred from the circuit 6 in thephoto-taking lens, the CPU 100 detects which of the focus detectionlight fluxes shown in FIGS. 6-(a) through 6-(d) corresponds to the sizeof the exit pupil TL₀ of the photo-taking lens TL based on the AFaperture value AFAV₀ which is related to the size of the exit pupil TL₀for detecting a focus condition. Based on the detected result, the CPU100 selects either of the focus detection modes so as to detect a focuscondition.

Accordingly, with respect to various kinds of photo-taking lenses, ifthe AFAV₀ thereof is great, a focus condition can be detected with ahigh accuracy by using a wide focus detection area Fa and even if theAFAV₀ is small, a focus condition can also be detected by using a narrowfocus detection area Fb. Thus, without reducing the kind of thephoto-taking lens capable of detecting a focus condition, a focuscondition can be detected with a high accuracy.

FIG. 1 shows the outline of the above-described construction. Based onthe result decided by a deciding means DM by using the lens datatransferred from the ROM 64 which stores lens information, a controlmeans CM switches the focus detection mode in a focus detecting meansFD. The focus detecting means FD, the deciding means DM, and the controlmeans CM are provided in the CPU 100.

The exit pupil TL₀ of the photo-taking lens TL also becomes small whenthe converter lens is mounted between the camera body and thephoto-taking lens. When the converter lens is mounted, the fully openaperture value of the lens in combination of the photo-taking lens withthe converter lens is changed with the change of the focal length madeby the converter lens. The conversion circuit 555 of the circuit 5 inthe converter lens converts the focal length, the fully open aperturevalue, and the AFAV₀ of the lens data inputted from the circuit 6provided in the photo-taking lens, thus outputting the converted valuesto the CPU 100. As described above, the CPU 100 selects either of thefocus detection modes using the AFAV₀.

In the state in which the converter lens is mounted, the position of theexit pupil is likely to change in the direction along the optical axisO_(p) and because of this, the size of the exit pupil TL₀ may change ata ratio different from the conversion ratio corresponding to the AFAV₀converted by the conversion circuit 555. As a result, despite that afocus condition can be detected in a wider range, a focus detection modein which a narrow focus detection area may be used is selected.

In order to overcome this problem, an off-axial focus detectionadmitting signal WB, which is data indicative of an admitting degreewith respect to a position of an exit pupil of the photo-taking lens, isstored in the lens ROM 64 of the circuit 6 in the photo-taking lens. Theadmitting signal WB is also transferred to the CPU 100 when lens data istransferred thereto. Further, based on the admitting signal WB, the CPU100 is so constructed that a standard value to be compared with theAFAV₀ for selecting a focus detection mode is made to be great so that afocus condition can be detected by a lens formed by combining aphoto-taking lens and a converter lens, which makes the AFAV₀ so greatthat it is impossible to detect a focus condition according to the knownmethod. In addition, the CPU 100 is so constructed that a focuscondition can be detected with high accuracy by lenses other than theabove-described lens because a focus detection area is greater than thatconventionally adopted.

That is, the ROM 64, which is the means for storing lens information, ofthe circuit 6 in the photo-taking lens also serves as a means forstoring as the admitting signal WB the degree of the influence in thevignetting in a light flux which is incident on a focus detecting systemAO, caused by the mounting of the converter lens on the photo-takinglens. The CPU 100 controls the operation of the focus detection means FDbased on the information stored in the ROM 64, namely, the admittingsignal WB.

The operation of the CPU 100 of the circuit 1 in the camera body isdescribed hereinbelow with reference to the flowcharts shown in FIGS. 7through 11.

FIG. 7 is a flowchart showing the main routine of the operation programof the CPU 100.

The operation of this main routine is started by the ON of the lightmeasuring switch SW1 caused by depressing the release button through thefirst half of its full stroke.

First, at step #706, a subroutine (reading of lens data) for reading thelens data from the circuit 6 in the photo-taking lens is called. In thissubroutine (reading of lens data), as described later, the followingoperations are performed: The read of the ROM data, the detection as towhether or not the photo-taking lens is mounted on the camera body, thedecision as to whether or not an automatic focus adjusting operation ispossible, and the decision of a focus detection mode due to theselection of a focus detection area to be used.

Next, at step #708, the subroutine AF for performing the automatic focusadjusting is called. In this subroutine AF, as described later, thephoto-taking lens is driven to obtain an in-focus state.

At step #710, the film sensitivity data SV of a film patrone put in thepatrone chamber of the camera body is read from the film sensitivityinformation circuit 360 into the CPU 100. At step #712, the lightmeasuring circuit 310 measures the luminance of the object and makes theA/D conversion of the luminous data obtained by the measuring, thusobtaining the data BV₀ of the luminance value. Thereafter, at step #714,an exposure calculation is performed according to the known method usinglens data, namely, the fully open aperture value AV₀ of the lens data,the minimum aperture value AVmax, the variation amount data ΔAV of theaperture value due to a zooming, the data of a focal length f, filmsensitivity data SV, and the luminance value data BV₀. At step #716, thevalue obtained by this exposure calculation is transferred to thedisplay circuit 340 so that the value is indicated thereby.

Next, at step #718, it is detected whether or not the light measuringswitch SW1 remains ON. If it is decided that the light measuring switchSW1 is OFF, the program goes to step #726 at which all the displays madeby the display circuit 340 are cleared, then the CPU 100 stops itsoperation at step #730.

If, on the other hand, it is detected that the light measuring switchSW1 remains ON at step #718, it is detected at step #720 whether or notthe release switch SW2 is OFF. If the release switch SW2 is ON, theknown release operation is performed at step #722. After the releaseoperation is completed, the state in which the light measuring switchSW1 is turned OFF is waited at step #724, then the program goes to step#726. If it is detected at step #720 that the release switch SW2 is OFF,the program returns to step #706 to repeat the operation of reading thelens data and the subsequent operations.

FIG. 8 is a flowchart of the subroutine (reading of lens data) to becalled in the main routine (step #706).

When this subroutine is called, first, at step #800, a lens mountingsignal ICP indicating that the photo-taking lens has been mounted isinputted. Only when the photo-taking lens is mounted on the camera body,the lens mounting signal ICP is outputted from the circuit 6 in thephoto-taking lens, i.e., if the photo-taking lens has not been mountedon the camera body, the lens mounting signal ICP is not inputted. Thelens mounting signal ICP allows the detection as to whether or not thephoto-taking lens has been mounted on the camera body.

At step #801, various lens data are inputted. The data to be inputtedare as follows: An axial focus detection signal FAEN₂ to be used todetect whether or not an axial focus detection is possible due to thevignetting of a focus detecting light flux in the vicinity of theoptical axis, for example in a reflecting telephoto lens the axial focusdetection is impossible; AF aperture value AFAV₀ to be used to decidewhether or not a focus detection light flux is vignetted by the exitpupil of a photo-taking lens; an AF lens deciding signal AFC to be usedto decide whether or not a lens drive mechanism for an automatic focusadjusting is mounted on a photo-taking lens; a converter lens mountingsignal CNVSET to be used to decide whether or not a converter lens ismounted on the photo-taking lens; an off-axial focus detection admittingsignal WB for switching a decision level according to the position ofthe exit pupil along the optical axis O_(p) in deciding which of aplurality of focus detection areas is possible for detecting a focuscondition according to the AFAV₀ ; an off-axial focus detection signalOFF_(ok) for deciding whether or not a focus condition can be detectedin off-axial focus detection areas; a coefficient K for finding thedrive amount of a photo-taking lens according to a defocus amountdetermined by a focus detection calculation; data AV₀ of a fully openaperture value to be used to the calculation of a light measuring; dataof a minimum aperture value AVmax; variation amount data ΔAV of aperturevalue caused by a zooming; and a focal length data f.

Thereafter, at step #802, the subroutine (decision as to whether or notAF is possible), for deciding whether or not an automatic focusingadjustment is possible using these five lens data (FAEN₂, AFAV₀, AFC,WB, OFF_(ok)), is called. At step #803, the subroutine (selection offocus detection mode), for determining a focus detection area which canbe used, is called. Thereafter, the program returns to the main routine.

FIG. 9 is a flowchart of the subroutine (decision as to whether or notAF is possible) to be called at step #802 of the subroutine (reading oflens data).

In this subroutine, the CPU 100 goes into an automatic focus adjustingmode (hereinafter referred to as AF mode) only when the conditions ofstep #900 through step #903 are all satisfied. At step #900, it isdetected whether or not the lens mounting signal ICP is outputted fromthe circuit 6 in the photo-taking lens. At step #901, it is detectedwhether or not a photo-taking lens allows a focus condition detectionusing an axial focus detecting light flux (FAEN₂ =1). At step #902, itis detected whether or not a photo-taking lens has an AFAV₀ which issmaller than a predetermined value J1 and that a focus detecting lightflux is not vignetted. At step #903, it is detected whether or not aphoto-taking lens is provided with a lens drive mechanism for anautomatic focus adjustment (AFC=1).

If the above conditions are all satisfied, AF mode is set at step #904.If all of the above conditions are not satisfied, a manual focusing modeis set at step #905, then the program returns.

FIG. 10 is a flowchart of the subroutine (selection of focus detectionmode) to be called at step #803 of the subroutine (reading of lensdata). The decision of the focus detection area according to thissubroutine is shown in FIG. 12.

In this subroutine, if it is detected that the converter lens is notmounted (CNVSET≠1) at step #1000, the program goes to step #1040. If theAFAV₀ is smaller than a predetermined value J3 at the step #1040, theprogram goes to step #1050. If it is decided that off-axial focusdetection areas can be used (OFF_(ok) =1) at step #1050, the multipointfocus detection mode in which three islands FA, FA₁, and FA₂ are used isset at step #1070.

If the AFAV₀ is greater than the predetermined value J3 at step #1040,the wide focus detection mode in which the entire block Fa of the firstisland FA is used is set at step #1080. If the AFAV₀ is greater than thepredetermined value J1, it is impossible to detect a focus condition, sothat the manual mode is set. This is shown by the subroutine (decisionas to whether or not AF is possible) at step #902 shown in FIG. 9.

Next, if it is detected at step #1000 that the converter lens is mounted(CNVSET=1), it is detected at step #1010 whether or not the off-axialfocus admitting signal WB is 1.

If no (WB≠1), it is detected at step #1030 whether or not the AFAV₀ isgreater than the predetermined value J4. If the AFAV₀ is smaller thanthe predetermined value J4, it is detected at step #1050 whether or nota focus condition can be detected using an off-axial focus detectionlight flux. If the focus condition can be detected using the off-axialfocus detection light flux (OFF_(ok) =1), the multipoint focus detectionmode is set at step #1070. If no, (OFF_(ok) =1), the wide focusdetection mode is set at step #1080. If it is decided at step #1030 thatthe AFAV₀ is greater than the predetermined value J4, it is detected atstep #1060 whether or not the AFAV₀ is greater than the predeterminedvalue J3. If the AFAV₀ is smaller than the predetermined value J3, thewide focus detection mode is set at step #1080. If it is decided at step#1060 that the AFAV₀ is greater than the predetermined value J3, thespot focus detection mode in which the partial block Fb disposed in thecenter of the first island FA is used is set at step #1090.

If it is detected that the off-axial focus admitting signal WB is 1 atstep #1010, the AFAV₀ is compared with the predetermined value J2 atstep #1020. If the AFAV₀ is smaller than the predetermined value J2, theprogram goes to step #1050. If it is detected at step #1020 that theAFAV₀ is greater than the predetermined value J2, the spot focusdetection mode is set at step #1090.

Either of the three focus detection modes is set at steps #1070, #1080,and #1090, then the program returns.

FIG. 11 is the subroutine of the subroutine AF to be called at step #708of the main routine.

When this subroutine is called, first, it is detected at step #1100whether or not the AF mode is selected. If it is decided that the AFmode is not selected, the program returns to the main routine withoutperforming an operation. If the AF mode is selected,, an integration isperformed on CCD at step #1105 and the resultant of the integration isinputted to the CPU 100 at step #1110, and the focus detection mode isdetected at steps #1115 and #1120.

If it is detected that the spot focus detection mode is selected at step#1115, the focus detection calculation at the spot focus detection modeis performed based on the resultant of the integration in the partialblock (Fb) of the island FA at step #1150. If it is detected that thewide focus detection mode is selected at step #1120, the focus detectioncalculation at the wide focus detection mode is performed based on theresultant of the integration in the entire block (Fa) of the island FAat step #1125. If it is detected that neither the spot focus detectionnor the wide focus detection is selected at steps #1115 and #1120, itmeans that the multipoint focus detection mode is selected. Accordingly,the calculation of a focus condition detection is performed in each ofthe islands FA, FA₁, and FA₂ at steps #1130 through #1140, then, thecalculation in which an island is selected from the three islands isperformed at step #1145.

The method for determining the island is based on the algorithm that, ofthe three islands, an island including an object nearest the camera isselected.

After the calculation for each of the focus detection modes at step#1155, it is detected whether or not the calculated focus condition isan in-focus condition. If the condition is the in-focus condition, thedisplay shown the in-focus condition is displayed on the display circuit340 at step #1160, then the program returns to the main routine. If thecalculated condition is not an in-focus condition, the lens drive amountis calculated at step #1165 using the coefficient K transmitted from thecircuit 6 in the photo-taking lens and the defocus amount calculated bythe focus detection calculation, then, the lens is driven at step #1170.Then, the program returns to step #1105 and repeats the above flow tillstep #1155. If it is decided that the in-focus condition is obtained atstep #1155, the program goes to step #1160. If it is decided that anin-focus condition is not obtained, the lens drives are repeated.

(Other embodiments)

Next, another embodiment will be described hereinbelow.

(1) The flowcharts shown in FIGS. 13 and 14 are other embodiments of thesubroutine (selection of focus detection mode) of the above-describedembodiment shown in FIG. 10. In these other embodiments, the number ofstandard values to be used for selecting a focus detection area by beingcompared with the AFAV₀ is smaller than that of the above-describedembodiment and the number of the focus detection modes to be selectedare two.

That is, in embodying the present invention, the focus detection mode isdivided into any desired number and the standard value to be comparedwith the AFAV₀ may be appropriately modified.

(2) The construction for dividing the focus detection area may beappropriately modified and the construction used in the above-describedembodiment may be replaced with a construction which radially dividesthe focus detection area such as a concentric or a matrix-shapedconstruction.

(3) In order to reduce the influence caused by a vignetting, amechanical means such as a projection provided on the mount portion maybe used to store information instead of the lens ROM 64 described in theabove-described embodiment.

As described above, in the camera system according to the embodiment,the storing means stores the degree of the influence of a vignetting ona light flux for a focus condition detection due to the mounting of theconverter lens on the photo-taking lens. The camera system also controlsthe operation of the focus detecting means based on the information,stored in the storing means, for correcting the influence of themovement of the exit pupil along the optical axis due to the mounting ofthe converter lens. Thus, the camera system in accordance with theembodiment is easily capable of determining whether or not a focuscondition can be accurately detected in a predetermined focus conditionarea, which enables a focus adjusting operation by using morephoto-taking lenses when a focus condition detection area consists of asingle area. If a focus condition detection area is divided into pluralareas, an accurate focus condition can be detected by using the greatestarea which can be used. Thus, the construction of the camera system fordetecting a focus condition with the converter lens mounted on thephoto-taking lens allows the use of various kinds of photo-taking lensand a more accurate focus condition detection.

Although the axial focus detection area is divided into two blocks Fa,Fb in the above-described embodiment, it may be used as only a singlearea without dividing as described below. That is, in the followingembodiment, the axial focus detection area is single and a zoom lens asthe photo-taking lens is mounted on the camera body without theconverter lens, as shown in FIG. 15. Since the most parts of thisembodiment are similar to those of the above-described embodiment shownin FIG. 1, like parts are designated by like reference numerals, so thatthe description of those parts will be omitted.

Referring to FIG. 15 showing the circuit diagram of a camera body of acamera system in accordance with this embodiment, a circuit 1 providedin the camera body and the circuit 11 provided in the zoom lens areelectrically connected to each other by a group of contacts 711 through715 mounted on the camera body and a group of contacts 921 through 925mounted on the zoom lens. The contacts 711 through 715 and 921 through925 are provided on a mount portion 9. The contacts 921 through 925correspond to the contacts 821 through 825 in FIG. 1.

The mount portions 7 and 8 are described hereinbelow. The mount portion9 provided between the camera body and the zoom lens comprises the mount71 provided on the camera body on which the zoom lens is mounted and amount 92 provided on the zoom lens. The circuit connection allows aserial communication between the CPU 108 in the circuit 1 provided inthe camera body and the circuit 11 provided in the zoom lens.

The zoom lens is used as a photo-taking lens. A zoom encoder 61 outputsa 3-bit coded signal ΔZ according to a zoom operation, namely, a focallength setting operation. A decoder 62 counts the clock pulse appliedfrom the clock output terminal 102 Sck of the CPU 108 and decodes it. Anaddress specifying circuit 63 selects the signals outputted from theencoder 61 and the decoder 62, thus specifying an address of a read onlymemory 66 (hereinafter referred to as ROM). The ROM 66 mounted on thephoto-taking lens previously stores the individual information on thephoto-taking lens in its addresses thereof. When an address of the ROM66 is specified by the address specifying circuit 63, the informationstored by the specified address is outputted in parallel from the ROM 66to a P/S conversion circuit 67. The P/S conversion circuit 67 convertsthe parallel signals outputted from the ROM 66 into serial signals, thusoutputting the serial signals to the input terminal 103 Sin of the CPU108 through mount contacts 923 and 713.

A constant voltage Vcc is supplied to the circuit 11 provided in thezoom lens (hereinafter referred to as zoom lens circuit) through themount contact 921 and the earth contact of the zoom lens circuit 11 isconnected to the earth line through the mount contact 925.

FIG. 16 shows images A₁₂, A₂₂, A₃₂, A₄₂, A₅₂, and A₆₂ of the apertureopenings A₁, A₂, A₃, A₄, A₅, and A₆ of the aperture mask AM on the exitpupil of various kinds of exchangeable lenses projected through thecondenser lens.

FIG. 16-(a) shows the case in which a photo-taking lens TL_(a) has agreat pupil. Since the pupil TL_(a0) thereof is great, all of theprojected images A₁₂, A₂₂, A₃₂, A₄₂, A₅₂, and A₆₂ exist on the exitpupil TL_(a0) of the photo-taking lens TL. And all light fluxes adaptedfor detecting a focus condition to an object, which are incident on theCCD line sensors P₀, P₀₁, and P₀₂, can be used because they are notvignetted by the pupil of the photo-taking lens TL_(a). That is, since afocus condition can be detected in all of the focus detection areas FA,FA₁, and FA₂ shown in FIG. 4 (refer to Table 2).

FIG. 16-(b) shows the case in which a photo-taking lens TL_(b) has asmall pupil. For example, a lens on which a teleconverter is attachedapplies to this case. Since the pupil TL_(b0) of this lens is small, alight flux without being vignetted by the pupil of the photo-taking lensTL_(b) is only an axial focus detection light flux. In this case, afocus condition can be detected only in the axial focus detection areaFa.

FIG. 16-(c) shows the case in which the position of the pupil TL_(e0) ofa lens changes. A shift lens applies to this case. If the shift amountof the lens is zero, a focus condition can be detected only in the axialfocus detection area FA, but as the shift amount increases to X₁ and X₂(0<X₁ <X₂), focus detection area which can be detected changes (refer toTable 2).

FIG. 16-(d) shows the case in which the configuration of the pupil ispeculiar such as that of a reflection telephoto lens. The portion shownby oblique lines indicates the portion in which a light flux isvignetted by a reflecting mirror (secondary mirror) of the reflectiontelephoto lens. In this case, the axial focus detection light fluxcannot be incident on the CCD line sensor P₀, so that a focus conditioncannot be detected in the axial focus detection area FA.

According to a reflection telephoto lens shown in FIG. 16-(e), the lightflux is vignetted by a reflecting mirror in a small extent. Therefore,the axial focus detection light flux is capable of being incident on theCCD line sensor P₀.

As described above, which of the focus detection areas can be useddepends on the kind of an exchangeable lens. In consideration of this,the lens ROM stores the individual information (focus detection signal)of the respective lenses as shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                                             Focus                                                                         Detection                                kind of Lens                                                                              P.sub.01, FA.sub.1                                                                     P.sub.01, FA.sub.1                                                                     P.sub.01, FA.sub.1                                                                   Signal                                   ______________________________________                                        Lens with   ◯                                                                          ◯                                                                          ◯                                                                        00H                                      Great Pupil                                                                   Lens with   X        ◯                                                                          X      01H                                      Small Pupil                                                                   Shift                                                                              Shift      X        ◯                                                                        X      01H                                    Lens Amount  ◯                                                         Shift      X        ◯                                                                        ◯                                                                        02H                                         Amount X.sub.1                                                                Shift      X        X      ◯                                                                        03H                                         Amount X.sub.2                                                                           ◯                                                 Re-   Type A    ◯                                                                          X      ◯                                                                        04H                                    flecting                                                                            Type B    X        ◯                                                                        X      01H                                    Tele-                                                                         photo                                                                         Lens                                                                          ______________________________________                                    

Table 2 shows focus detection areas FA, FA₁, and FA₂ as well as thecorresponding CCD line sensors P₀, P₀₁, and P₀₂ which can be useddepending on the kind of a lens and the focus detection signals. Thefocus detection areas indicated by "O" and the CCD line sensors disposedin correspondence thereto can detect a focus condition. The focusdetection signals consist of 8-bit data.

FIG. 17 shows the relationship between the best focal plane positions atwhich film is located and the focus position detected by the CCD linesensor (hereinafter referred to as AF sensor) under visible and infraredlight. The axis of abscissa X indicates optical axis, in which the leftside indicates the direction (+ direction) of the photo-taking lens andthe right side shows the direction (- direction) of the film surface.The axis of ordinate Y shows the distance from the optical axis on theplane perpendicular to the optical axis. At the position shown by "OnAxis" an image performance of the lens by a light on the axis (incidentlight parallel to optical axis) is most favorable. If a film is disposedin this position, an aberration performance with respect to a light outof the axis (incident light oblique with respect to the optical axis) isunfavorable. Therefore a favorable defocus amount cannot be obtained bya focus condition detection using an off-axial focus detection lightflux. In order to overcome this problem, the film is located slightlydistant best focal plane position from the position shown as the " OnAxis" in consideration of the axial light and the off-axial light. Inthe curve shown as an image, the contrast of image by an actual lightwhich passes through the photo-taking lens is most favorable (forexample, F=2.0).

As described above, the AF sensor detects a focus condition using theaxial focus detection light flux or an off-axial focus detection lightflux, which has the effect equivalent to the fact that the aperturevalue of the photo-taking lens becomes great. Therefore, the aberrationperformance given on the AF sensor is more favorable than that of thephoto-taking lens. The in-focus determining position to be made by theAF sensor is shown in FIG. 17 as the stop position of the AF sensorunder a visible light or an infrared ray. When a focus condition cannotbe detected under a visible light, an infrared ray is emitted from acomplementary light emitting circuit provided in the camera body. Thus,the focus condition can be detected by the infrared ray. Thecomplementary light emitting circuit may be mounted on a device outsidethe camera body, for example, on an electronic flash emitting device.

Thus, there is a dislocation between the AF sensor stop position and thebest focal plane position, and the dislocation amount changes accordingto the distance from the optical axis (image height). Therefore,according to the present invention, the focus condition detected by theAf sensor is corrected based on the dislocation amounts ΔSB_(on),ΔSB_(off), Δsb_(off), ΔIR_(on), ΔIR_(off), and Δir_(off) stored in thelens ROM which are shown in FIG. 17. Suffix ON means a correction amounton the focus detection area FA in which a focus condition is detectedusing the axial focus detection light flux. The suffix OFF means acorrection amount on each of the focus detection areas FA₁, FA₂ in whicha focus condition is detected using the off-axial focus detection lightflux. Since the areas FA₁ and FA₂ are symmetrical with respect to theoptical axis, the focus condition can be corrected using the samecorrection data.

In FIG. 17, ΔSB denotes the dislocation amount of the defocus amountbetween the AF sensor stop position and the best focal plane positionunder a visible light; Δsb_(off) designates the dislocation amount ofdefocus amount between the AF sensor stop position on the optical axisand on the off-axial position under a visible light; ΔIR indicates thedislocation amount of defocus amount between the AF sensor stop positionunder an infrared ray under a visible light and Δir_(off) denotes thedislocation amount of defocus amount between the AF sensor stop positionon the optical axis and on the off-axial position.

Since these dislocation amounts ΔSB and ΔIR are varied by the zooming orfocusing of the photo-taking lens, the difference amounts according tothe zooming or the focusing are stored in the lens ROM as a correctionamount. But since the dislocation amount Δsb_(off) and Δir_(off) arehardly varied by the zooming or the focusing, this dislocation amountmay be stored in the lens ROM as a fixed value.

As shown by arrows in FIG. 17, ΔSB_(on), ΔSB_(off), ΔIR_(on), andΔIR_(off) are positive correction amounts and Δsb_(off) and Δir_(off)are negative correction amounts.

If the correction amounts ΔSB and ΔIR are varied by the focusing,similarly to the zoom encoder 61 shown in FIG. 15, an encoder fordetecting a focal length may provided in the lens, whereby the addressof the ROM may be designated according the outputs of this encoder andthe decoder 62.

The operation of the CPU 108 provided in the camera body is describedwith reference to the flowchart shown in FIG. 18 through FIG. 29.

FIG. 18 is a flowchart showing the main routine of the operation programof the CPU 108. When the switch SW₁ is ON by the depression of theshutter release button to the first half of its full stroke, the programis initiated from step #1700, then, flags shown in Table 3 are reset to0 at step #1702.

The flags to be used in the CPU 108 are described in Table 3. Thedetailed descriptions of the flags are made later.

                  TABLE 3                                                         ______________________________________                                              Name of                                                                 Flag  Flag        1              0                                            ______________________________________                                        F1    Read Flag First Reading ROM                                                                            Reading ROM Data                                               Data after Initiation of                                                                     after First Reading                                            CPU                                                           F2    Lens      Conventional Lens                                                                            New Lens                                             Generation                                                                    Flag                                                                    F3    Lens Flag Lens Mounting  Lens Non-mounting                                              Condition      Condition                                      F4    Serial    Read Processing of                                                                           Read Procesing of                                    Flag      Serial Data by 1-byte                                                                        Serial Data is not                                             is completed   completed                                      AFF   AF Flag   AF Operation   AF Operation                                                   is not performed                                                                             is performed                                   LCF   Low       Focus Condition                                                                              Focus Condition                                      Contrast  cannot be detected                                                                           can be detected                                      Flag                                                                    LCF.sub.1                                                                           Low       Focus Condition                                                                              Focus Condition                                      Contrast  cannot be detected                                                                           can be detected                                      Flag 1    in Area FA.sub.1                                                                             in Area FA.sub.1                               LCF.sub.2                                                                           Low       Focus Condition                                                                              Focus Condition                                      Contrast  cannot be detected                                                                           can be detected                                      Flag 2    iin Area FA    in Area FA                                     LCF.sub.3                                                                           Low       Focus Condition                                                                              Focus Condition                                      Contrast  cannot be detected                                                                           can be detected                                      Flag 3    in Area FA.sub.2                                                                             in Area FA.sub.2                               F5    Comple-   Complementary Light                                                                          Complementary                                        mentary   is emitted     Light is not                                         Light Flag               emitted                                        ______________________________________                                    

At step #1704, since the data stored in the ROM is first read after theCPU is initiated, a read flag F1 is set to 1, then the program goes to asubroutine, for reading lens data, of step #1706. As described later, inthis subroutine for reading the lens data, the data stored in the ROM isread, whether or not the lens is mounted and a lens generation aredetected. Thereafter, the program returns to the main routine.

Then, the program goes to an automatic focus subroutine (hereinafterreferred to as AF subroutine) at step #1708. As described later, in theAF subroutine, the focus condition is detected, i.e., the photo-takinglens is driven to be in-focus condition.

At step #1710, the data of a film sensitivity is read into the CPU 108through the film sensitivity information circuit 360. At step #1712, thelight measuring of the luminance of the field and an A/D conversionthereof are performed by the light measuring circuit 310 so as to obtainthe data of the luminance value. Based on these data, an exposurecalculation is performed according to the known method at step #1714,then the calculated exposure data is transferred to the display circuit340 which displays the data at step #1716.

Next, it is detected at step #1718 whether or not the switch SW1 stillremains ON. If the switch SW1 is OFF, the program goes to step #1726 atwhich the display of the display circuit 340 is all cleared, and theread flag F1 is reset to 0 at step #1728, and then, the CPU 108 entersinto a sleep state at step #1730.

If it is decided at step #1718 that the switch SW1 is ON, it is detectedat step #1720 whether or not the switch SW2, which is turned on when thebutton is completely depressed through the full stroke, is ON. If theswitch SW2 is ON, the known release operation is carried out at step#1722. After the release operation is completed, the proceeding of theprogram is waited at step #1724 until the switch SW1 becomes OFF, thenthe program goes to step #1726. If it is detected at step #1720 that theswitch SW2 is OFF, the program returns to step #1706 so as to repeat theoperation starting from read of the lens data.

The flowchart shown in FIG. 19 shows the subroutine for reading lensdata with respect to step #1706 in FIG. 18. It is detected at step #1802whether or not the read flag F1 is 1 or 0, i.e., it is detected whetheror not the data of the ROM is read for the first time or twice or moreafter the CPU is initiated. If it is detected that the data of the ROMis read for the first time, the program goes to step #1804. If it isdetected that the ROM has been read twice or more, the program goes tostep #1822.

Before proceeding to the description of the read operation, the lensinformation stored in the lens ROM is described hereinbelow withreference to FIG. 30. The ROM in the exchangeable lens stores individuallens information necessary for such as an exposure control and AFcontrol at each specified address thereof as 8-bit digital data. Butwith the increase of the functions of the camera system due to thedevelopment of the camera system, the information (conventional data)stored in the ROM provided in the conventional lens does not allow thecamera to control the developed function. In this respect, the ROM whichhas stored the information (new data) on the new function in addition tothe conventional information may be provided in the developed new lensto control the developed function. FIG. 30 is a comparison view of thearea map for comparing the conventional lens and the new lens.

The information d₁ through d_(i) (conventional data) of the conventionallens is stored by the ROM provided in the conventional lens at theaddresses of 1 through i and the lens information d_(n) (data foridentifying the kind of the lens) is stored at the last address of n. Nolens information is stored at the addresses of i+1 through n-1, namely,vacant addresses. The ROM mounted on the new lens has the same capacityas the ROM provided in the conventional lens. The new ROM stores theconventional data d₁ through d_(i) at the addresses of 1 through i, newlens information d_(i+1) through d_(j) (new data) at the addresses ofi+1 through j and the data dn for identifying the kind of the lens atthe last address of n.

In the lens defined as the conventional lens in accordance with thepresent invention, the dislocation amount ΔSB_(on), ΔIR_(on) between thebest focal plane position and the AF sensor stop position is stored inthe lens ROM as the correction amount only on the focus detection areaFA in which a focus condition is detected using the axial focusdetection light flux (refer to Table 4). On the other hand, thedislocation amount ΔIR_(off), ΔSB_(off) or Δir_(off), Δsb_(off) on thefocus detection areas FA₁ and FA₂ are also stored in the lens ROM in thenew lens.

Returning to FIG. 19, description is made with regard to the operationof reading the data of the ROM to be performed if the read flag F1 is 1at step #1802, namely, the operation of reading the data of the ROM forthe first time after the CPU 108 is started. Since this is the firsttime read, the number n of all the addresses number of the ROM is set tothe serial data counter N at step #1804 as the number of read data. Atstep #1806, according to the subroutine for reading the data into thecamera body, n pieces of ROM data corresponding to the current lenscondition due to a zooming or a focusing are stored in the RAM providedin the camera body. Thus, the first time read is completed. Then, theread flag F1 is reset to 0 at step #1808.

The data called ICP is stored by the ROM at the first address thereof.Of eight bits, the high-order two bits consist of the data for detectingwhether or not the lens is mounted on the camera body and the remainingsix bits consist of lens generation identifying data which indicateswhether the lens is conventional or new. It is detected at step #1810whether or not the lens is mounted on the camera body utilizing thehigh-order two bits of the ICP. If the lens is not mounted on the camerabody, the program goes to step #1836 at which the lens flag F3 is resetto 0 to indicate the non-mounting of the lens, and at step #1838, the AFflag AFF is set to 1 to indicate that the AF operation is not effected.Then, the program returns.

If it is decided at step #1810 that the lens is mounted on the camerabody, the lens flag F3 is set to 1 at step #1812 so as to indicate thatthe lens is mounted, then the program goes to step #1814 at which thelens generation is identified. It is detected at step #1814 whether thelens mounted on the camera body is conventional or new utilizing theremaining six bits of the ICP. If it is decided that the lens is new,necessary information is all stored in the RAM provided in the camerabody, then the program goes to step #1816 at which the lens generationflag F2 is reset to 0. Thereafter, the program returns. When the lensgeneration flag F2 is set to 1, it indicates that the conventional lensis mounted on the camera body. When the lens generation flag is 0, itindicates that the new lens in mounted on the camera body.

If it is decided at step #1814 that the lens mounted on the camera bodyis conventional, the lens generation flag F2 is set to 1 at step #1818and new data not stored in the ROM is read at step #1820 from data tableprovided in the camera body according to the subroutine for referencingthe data table provided in the camera body. Then, the program returns.

If it is decided that the read flag F1 is 0 at step #1802, it means thatthe CPU 108 has read the ROM data once or more. Then, it is detected atstep #1822 the lens mounted on the camera body is conventional or newusing the lens generation flag F2. If it is decided that the lens isnew, the number j is set to a serial data counter N at step #1824 as thenumber of read data of the ROM. If it is decided that the lens mountedon the camera body is conventional, the number i is set to the serialdata counter N at step #1826. Then, similarly to the operation to beperformed at step #1806, the read subroutine for reading the data intothe RAM in the camera body is executed at step #1828. As describedabove, it is to be noted that j>i. Thus, the period for reading the dataof the ROM is shortened by selecting the number of read data.

Similarly to step #1810, at step #1830, it is detected whether or notthe lens is mounted on the camera body according to the read ICP data.If it is decided that the lens is mounted on the camera body, theprogram goes to step #1832 at which the lens flag F3 is identified todetect whether or not the lens was mounted on the camera body at theprevious read of the lens data. If it is decided that lens flag F3 is 0,it means that the lens was not mounted on the camera body at theprevious read of the lens data and the lens is mounted thereoncurrently, so that the lens flag F3 is set to 1 at step #1834, whichindicates that the lens is mounted. Then, the program goes to step #1804so as to read n pieces of ROM data again.

The flowchart shown in FIG. 20 is the read subroutine for reading theROM data into the RAM in the camera body, according to the steps #1806and #1828 in FIG. 19. First, at step #1902, the address m₀ is set to theaddress pointer of the RAM. Similarly to the ROM, the RAM consists ofeight bits. Next, at step #1904, the serial flag F4 is reset to 0 toindicate that the read processing of the serial data of the ROM is notcompleted, then set 8 to the serial counter 120 shown in FIG. 2-(b) atstep #1906 so that the serial counter 120 counts the clock pulse ofeight bits.

When the output terminal CS shown in FIG. 2-(b) becomes a low level atstep #1908, the serial communication is possible between the camera bodyand the lens. When the serial port control register SCKC is set to 1 atstep #1910, clock pulse starts to be outputted from the clock outputterminal Sck shown in FIG. 2-(b). At step #1912, the interruption iswaited, that is, the state that the serial flag F4 becomes 1 as a resultof the interruption, i.e., the read of the 1-byte serial data of the ROMinto the RAM is waited.

The processing operation of the serial interruption is described withreference to FIG. 21. When the serial counter 120 completes the countingof eight clock pulses, it produces an interruption signal INT which istransferred to the CPU 108. That is, while the CPU 108 waits until theserial flag F4 becomes 1 at step #1912 shown in FIG. 20, the serialcounter 120 completes the counting of eight clock pulses and generatesthe interruption signal INT, then the program goes to the steps shown inFIG. 21. First, at step #2002, the serial port control register SCKC isreset to 0 so that the clock pulse is not outputted from the camera bodyto the lens. Next, at step #2004, the 8-bit data of the predeterminedaddress of the ROM read into the serial register 121 is transferred tothe address (first time, m₀) specified by the address pointer M providedin the RAM so as to be stored therein. At step #2006, the addresspointer M which specifies the address in the RAM is advanced by one. Atstep #2008, the serial flag F4 is set to 1 to indicate that the read ofthe 1-byte serial data of the ROM into the RAM has been completed. Atstep #2010, the serial counter 120 is set to 8 to read the subsequentdata of the ROM, then the program returns to step #1912 shown in FIG.20.

Since it is decided at step #1912 that the serial flag F4 is set to 1,the program goes to step #1914 at which 1 is subtracted from the serialdata counter N, then, at step #1915, the serial flag F4 is reset to 0again.

At step #1916, it is detected whether or not all the ROM data indicatedby the number set to the serial data counter N has been stored in theRAM provided in the camera body. If all the ROM data has been read, Nbecomes 0, so that at step #1918, the output terminal CS is set to ahigh level to permit the completion of the communication between thecamera body and the lens. Then, the program returns. If all the data hasnot been read, the program returns to step #1910 to read the next ROMdata.

The flowchart shown in FIG. 22 is the subroutine for referencing thedata table provided in the camera body,

according to the step #1820 in FIG. 19. This subroutine shows theoperation of storing the lens information (new data) not stored in theconventional lens in the RAM provided in the camera body with referenceto the data table in the camera body when the conventional lens ismounted on the camera body.

FIG. 31 shows an area map of the data table provided in the camera body.The n address which is the last address of the lens ROM stores the datadn for identifying the kind of the lens regardless of whether the lensis conventional or new. The data dn for identifying the kind of the lenshas any one of the values dn₁ through d_(ne) depending on the kind ofthe lens. The data table provided in the camera body stores data (di+1through dj) corresponding to the new data stored in the new lensaccording to the kind of the conventional lens.

Returning to the flowchart shown in FIG. 22, first, at step #2102, theCPU 108 receives the data dn for identifying the kind of the lens fromthe RAM. Based on the received data dn=dnk (1≦k≦l), the counter K is setto the data table area number k at step #2104. At step #2106, the serialdata counter N is set to the number j-i which is the number of thereference data transferred from the data table provided in the camerabody. At step #2108, the address pointer M of the RAM is set to thefirst address PG,71 number m₀ +i. The conventional data stored in theROM already is stored in the RAM at the address number of m₀ ˜m₀ +i-1.

At step #2110, 1-byte data dj+1 corresponding to the counter K isreferenced from the data table provided in the camera body, thus beingstored in the RAM at the address specified by the address pointer M.Similarly to the subroutine for reading the lens data, the data dj+1through dj is referenced from data table provided in the camera body byone byte, thus being stored in the RAM.

Table 4 shows only the data, to be used in the embodiment, of the lensinformation to be stored in the RAM of the camera body. The addresses isshown in the Table 4 for convenience' sake. As described above indetail, in the conventional lens, the lens information of at least theaddresses of 1 through 5 and n stored in the RAM are stored in the ROM.And in the new lens, the lens information of the addresses of 1 through5, i+1 through i+4, and n stored in the ROM are stored in the ROM. Inthe conventional lens, the lens information corresponding to theaddresses of i+1 through i+4 is read from the data table provided in thecamera body depending on the kind of the conventional lens and is storedin the RAM. "Variable" shown in the Table 4 means that the data isvaried by a zooming or a focusing. If a lens is not a shift lens, theshift amount of the shift lens is fixed to zero.

                  TABLE 4                                                         ______________________________________                                        Stored Area in ROM                                                                            Lens Information                                              ______________________________________                                        Conventional Data                                                                         1       Lens Mounting Signal ICP                                  (From ROM)  2       Fully Open Aperture Value AV0                                         3       ΔSB.sub.on (Variable)                                           4       ΔIR.sub.on (Variable)                                           5       Conversion Coefficient K                                  New Data    i + 1   AF Detection Signal                                       (From ROM or                                                                              i + 2   ΔSB.sub.off (Variable) or Δsb.sub.off                             (Fixed)                                                   Data Table in                                                                             i + 3   ΔIR.sub.off (Variable) or Δir.sub.off                             (Fixed)                                                   Body)       i + 4   Shift Amount of Shift Lens                                Address of n                                                                              n       Data for identifying kind of Lens                         ______________________________________                                    

FIG. 23 is a flowchart showing the AF subroutine of step #1708 shown inFIG. 18.

At step #2202, the state of an AF flag AFF is detected. The AF flag AFFis set to 1 at step #1810 or #1830 shown in FIG. 19 when the lens is notmounted on the camera body or set after an in-focus condition isobtained as described later. That is, when the AF flag AFF is set to 1,it means that an in-focus condition has been obtained or the lens hasnot been mounted on the camera body. Therefore, the program returns tostep #2246 without carrying out a focus detecting operation. If the AFflag AFF is 0, the state of the complementary light flag F5 is detectedat step #2204. If the complementary light flag F5 is set to 1, theprogram goes to steps #2218 through #2232 at which a focus detectingoperation is performed using the complementary light.

If the complementary light flag F5 is 0 at step #2204, the integrationsare performed by the AF sensors (CCD line sensor) P₀, P₀₁, and P₀₂ atstep #2206 according to the known method and the integrated data isdamped at step #2208.

Step #2210 is the subroutine for, using the integrated data, calculatinga focus detection. The operation of this subroutine is described withreference to the flowchart shown in FIG. 24. At step #2302, the focusdetections are calculated in each of the focus detection areas FA, FA₁,and FA₂. In calculating the focus detection, the calculation of thecontrast of the object and the correlation calculation are performed byusing the signals of AF sensors to create the data which is necessaryfor deciding whether or not the focus condition can be detected and thedata indicating the reliability of the detected focus condition. Thedetailed description of the calculating method is described in, forexample, in Japanese Laid-Open Patent Publication No. 60-4914, theapplication of which was filed by the present applicant.

At step #2304, low contrast flags LCF, LCF₁, LCF₂, and LCF₃ are reset to0. These low contrast flags indicate whether or not the focus conditioncan be detected. If they are 1, it indicates that the focus conditioncannot be detected, and if 0, it indicates that the focus condition canbe detected. On the other hand, the AF detection signal stored in thelens ROM specifies a focus detection area which can be used depending onthe configuration of a lens irrespective of the result of thecalculation of the focus condition detection.

At step #2306, it is detected whether or not a focus condition has beenable to be detected in the focus detection area FA₁ based on the focuscondition detection calculated by the AF sensor P₀₁ arranged incorrespondence with the focus detection area FA₁. If it is decided thatthe focus condition detection has been able to be detected, no operationis performed. If the focus condition has been able to be detected, thelow contrast flag LCF₁ for the area FA₁ is set to 1 at step #2308, thenthe program goes to step #2310. At step #2310 through step #2316, it isdetected whether or not focus condition has been able to be detected inthe areas FA and FA₂.

Next, at step #2318, the CPU 108 receives AF detection signal stored inthe RAM provided in the camera body. If received data is 00H, theprogram goes to step #2320. If data is 01H, the program goes to step#2330. If data is 02H, the program goes to step #2336. If data is 03H,the program goes to step #2344. If the data is 04H, the program goes tostep #2350 (refer to Table 2). It is detected in each of the above flowswhether or not the focus condition has been able to be detected, in eachof the focus condition detection areas specified by the AF detectionsignal, referring to the low contrast flag for the area. If the focuscondition has not been able to be detected according to the calculationsof the focus condition detections in all the focus detection areasspecified by the AF detection signal, the low contrast flag LCF is setto 1, then the program returns. On the other hand, if the focuscondition has been able to be detected in one or more detecting areas,the program returns. For example, if the CPU 108 receives 02H as the AFdetection signal, the program goes from step #2318 to step #2336. Sincethe AF detection signal 02H specifies FA and FA₂ as the focus detectionareas, it is detected based on the low contrast flags LCF2 and LCF3whether or not the focus condition has been able to be detected. If itis decided at step #2338 that the low contrast flag LCF2 is 0, the focuscondition has been able to be detected at least in the focus detectionarea FA. Therefore, the program returns. If the low contrast flag LCF2is 1 at step #2338 and if the low contrast flag LCF3 is 0 at step #2340,the focus condition has been able to be detected at least in the focusdetection area FA₂. Then, the program returns. If both low contrastflags are 1, the focus condition has been able to be detected in all theareas, so that the low contrast flag LCF is set to 1 at step #2342, thenthe program returns. A similar operation is performed when other AFdetection signals are received.

Returning to the flowchart shown in FIG. 23, at step #2212, it isdetected whether or not the focus condition has been able to be detectedbased on the low contrast flag LCF determined in the subroutine forcalculating the focus condition detection. If the low contrast flag LCFis 1, the focus condition has not been able to be detected in any of theareas. Accordingly, the complementary light flag F5 is set to 1 at step#2216, then the program goes to step #2218 and the steps subsequentthereto at which the focus detecting operation is performed using thecomplementary light. When the contrast of the object is very low or theluminance thereof is very low, it is impossible to detect a focuscondition. Therefore, at steps subsequent to step #2218, the integrationof the received light is performed by emitting the complementary lightfrom the complementary light circuit 350 provided in the camera body.The calculation for detecting the focus condition to be performed atsteps #2226, #2228 and the detection as to whether or not the focuscondition has been able to be detected are carried out similarly to theoperation to be performed at step #2210 and #2212. If the focuscondition has not been able to be detected even if the integration ofthe received light is performed by emitting the complementary light, awarning that the focus condition has not been able to be detected isdisplayed by the display circuit 340 at step #2232, then the AF flag AFFis set to 1. Thereafter, the program returns to steps #2240 and #2246.

The subroutine for calculating a defocus amount to be performed at step#2214 or #2230 is described with reference to the flowcharts shown inFIGS. 25 through 28.

The flowchart shown in FIG. 25 is one embodiment of the subroutine forthe defocus amount calculation A under a visible light. At step #2402through step #2406, a defocus amount is calculated in the focusdetection area FA₁. The state of the low contrast flag LCF1corresponding to the focus detection area FA₁ is detected at step #2402.If the flag LCF1 is 1, the focus condition has not been able to bedetected in the area FA₁, i.e., the defocus amount cannot be calculated,so that the program goes to step #2408. At step #2404, the defocusamount Δξ1 is calculated based on the result obtained by the calculationfor detecting a focus condition. As described above with reference toFIG. 17, there is a dislocation amount between the best focal planeposition which is the actual film face and the AF sensor stop position.Accordingly, the defocus amount Δξ1 obtained by the calculation fordetecting the focus condition based on the output of the AF sensor isaccurately incapable of displaying the best focal plane position.Therefore, at step #2406, a correcting calculation to form the image onthe best focal plane position is performed. That is, the correction ismade by the following calculation.

    Δξ1'=Δξ1+ΔSB.sub.on +Δsb.sub.off(1)

where ΔSB_(on) is conventional and variable data caused by a zooming ora focusing, Δsb_(off) is new and fixed data which does not change due tothe zooming or the focusing.

Similarly, at step #2408 through #2412, the defocus amount in the focusdetection area FA is calculated. The defocus amount Δξ2 obtained by thecalculation for detecting the focus condition is corrected by thefollowing calculation.

    Δξ2'=Δξ2+ΔSB.sub.on                (2)

That is, since the focus condition is detected in the focus detectionarea FA using axial focus detection light flux, the defocus amount iscorrected using only conventional data ΔSB_(on) which is variable.

At step #2414 through #2418, the defocus amount in the focus detectionarea FA₂ is calculated. The correcting calculation is the same as theequation (1):

    Δξ3'=Δξ3+ΔSB.sub.on +Δsb.sub.off(3)

The feature of the subroutine for the calculation A of the defocusamount under a visible light is that variable data for the off-axis iscreated utilizing the variable data ΔSB_(on) for the optical axis storedin the ROM provided in the conventional lens as the conventional data.Therefore, the data to be newly stored is only the fixed data ΔSboff. Inthe focus detection areas FA₁ and FA₂, a focus condition is detectedbased on a light flux which pass through the areas symmetrical withrespect to the optical axis of the lens. Therefore, the memory of onecorrection amount Δsb_(off) is enough to be used to perform a correctingcalculation.

The flowchart shown in FIG. 26 is one embodiment of the subroutine ofstep #2230 at which the calculation A of the defocus amount is performedusing a complementary light. Similarly to the calculation for correctingthe defocus amount under a visible light in FIG. 25, new variable datais created using the new fixed data and the conventional variable data.Since the flow in this subroutine is the same as that shown in FIG. 25,only the correcting calculation is described hereinbelow.

When a focus condition is detected under an infrared light as acomplementary light, the chromatic aberration of the lens necessitatesan another correction other than the correction under a visible light(refer to FIG. 17). The correction of the defocus amount Δξ2 isperformed by the following equation:

    Δξ2'=Δξ2+ΔSB.sub.on +(a×ΔIR.sub.on +b)(4)

where ΔIR_(on) is conventional data which is variable by a zooming or afocusing; and (a) is a correction coefficient, showing the ratio of thecorrection amount ΔIR_(on) ' in the wavelength of an infrared light usedas the complementary light to the correction amount ΔIR_(on) obtainedunder an infrared light whose wavelength is 800 nm. The correctionamounts ΔIR_(on) stored in the conventional lens and the new lens arethe correction amount under the wavelength of 800 nm. Therefore, whenthe object is illuminated by a complementary light having the wavelengthother than 800 nm, a correction which corresponds to the used wavelengthis necessary. The reason why the ratio of ΔIR_(on) ' to ΔIR_(on) is usedas the correction coefficient (a) is because the chromatic aberration ofthe photo-taking lens changes linearly in the infrared wavelength regionand because this ratio is not changed greatly by a zooming or afocusing. Reference symbol (b) in the above equation (4) denotes thecharacteristic for the infrared ray in the AF sensor module (block AFMOshown by dotted lines shown in FIG. 3), namely, the ΔIR correction valueof the AF sensor module. The correction coefficient (a) or thecorrection value (b) are stored in the E² PROM provided in the camerabody.

The correction of the defocus amount Δξ obtained in the focus detectionareas FA₁ or FA₂ is made by the following equation:

    Δξ'=Δξ+ΔSB.sub.on +(a×ΔIR.sub.on +b+Δir.sub.off)                                     (5)

where Δir_(off) is new data which is not varied by a zooming or afocusing. The new data to be stored is only the data Δir_(off).

The flowchart shown in FIG. 27 is the subroutine for the calculation Bof a defocus amount under a visible light. This subroutine is anotherembodiment of the flowchart shown in FIG. 25. This embodiment ischaracterized in that new variable data ΔSB_(off) is previously storedin the ROM or the data table. That is, the defocus amounts Δξ obtainedin the focus detection areas FA₁ and FA₂ are corrected as follows:

    Δξ'=Δξ+ΔSB.sub.off                 (6)

The correction of the defocus amount in the focus detection area FA ismade by the equation (2) shown above in which the correction data of theaxial focus detection light flux ΔSB_(on) is used.

Needless to say, the capacity of the ROM for storing new data mustincrease. This embodiment is effective for the lens in which thedifference amount Δsb_(off) between the AF sensor stop position on theoptical axis and that out of the optical axis is greatly changed by azooming or a focusing.

The flowchart shown in FIG. 28 is the subroutine for the calculation Bof a defocus amount using a complementary light. This subroutine isanother embodiment of the flowchart shown in FIG. 26. Similarly to theembodiment corresponding to the flowchart shown in FIG. 27, dataΔIR_(off) which is varied by a zooming or a focusing is stored as newdata. The defocus amount Δξ obtained in the focus detection area FA₁ orFA₂ is corrected as follows:

    Δξ'=Δξ+ΔSB.sub.on +(a×ΔIR.sub.off +b)(7)

The correction of the defocus amount in the focus detection area FA ismade by the equation (4) shown above.

Returning to the flowchart shown in FIG. 23, step #2234 is a subroutinefor calculating the controlling defocus amount necessary for driving thelens according to the corrected defocus amount of plural focus detectionareas obtained at step #2214 or #2230. It is detected at step #2236based on the calculated controlling defocus amount whether or not thecurrent lens position is in an in-focus condition. If the lens is in thein-focus condition, the display circuit 340 displays at step #2238 thatthe lens is in the in-focus condition, then the program goes to step#2240. If the lens is not in the in-focus condition, a necessary lensdrive amount is calculated at step #2242 according to the controllingdefocus amount and the conversion coefficient K stored in the ROM sothat the lens is driven at step #2244, then the program goes to step#2238.

The flowchart shown in FIG. 29 shows in detail a subroutine forcalculating a controlling defocus amount with respect to step #1234shown in FIG. 23. First, the AF detection signal stored in the RAM inthe camera body is received at step #2802. In accordance with the data,the program goes to the flows. For example, if the AF detection signalis 00H, the controlling defocus amount for driving the lens iscalculated by the equation Δξ=f(Δξ1', Δξ2', Δξ3') to be performed atstep #2806. The function f selects an effective defocus amount from thedefocus amounts Δξ1', Δξ2', and Δξ3' of plural focus detection areas andcalculates the controlling defocus, amount according to thepredetermined evaluation algorithm. If the AF detection signal is 01H,the defocus amount Δξ2 detected in the focus detection area FA isadopted as the controlling defocus amount at step #2810. When the AFdetection signal is 02H, 03H or 04H, the controlling defocus amounts arecalculated according to the respective flows. The detailed descriptionthereof is described, for example, in Japanese Laid-Open PatentPublication No. 61-55618, the application of which was filed by thepresent applicant.

As described in detail, in the focus detecting system of thelens-exchangeable camera according to the embodiment, the storing meansstores the first correction amount with respect to the aberration of theexchangeable lens when a focus condition is detected to an object on theoptical axis, and the second correction amount with respect to theaberration of the exchangeable lens when a focus condition is detectedto an object out of the optical axis, The first correction amount isused to correct a defocus amount obtained when the focus condition of anobject present in an area in the vicinity of the optical axis of theexchangeable lens is detected, and the first and second correctionamounts are used to correct a defocus amount obtained when the focuscondition of an object present in an area out of the optical axis of theexchangeable lens is detected. Accordingly, the focus conditions of theobjects present in both areas can be detected with a high accuracy.

In above embodiment, although the ROM in the new lens or the data tablein the camera body stored the information with respect to the focuscondition detection, the data table can store the information withrespect to the exposure measurement, too. For example, if the exposuremeasurement region in the conventional camera system is all of the imageplane and that in the new camera system is divided into plural areas onthe image plane, deviation data, for the exposure measurement at openaperture between the conventional region and each of the new dividedareas, are stored.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. A camera system having a camera body and firstand second lenses exchangeable to said camera body, comprising:saidfirst lens comprising means for outputting first data which indicatessaid first lens belongs to a first lens type and fourth data dependingon the characteristic of said first lens; said second lens comprisingmeans for outputting second data which indicates said second lensbelongs to a second lens type and third data depending on thecharacteristic of said second lens, types of data in said third dataincluding all types of data in said fourth data; said camera bodycomprising:means for inputting the data from the outputting means ofsaid first or second lens attached to said camera body, means fordiscriminating the lens type based on whether the inputted data is thefirst or second data, means for storing fifth data depending on thecharacteristic of the lens belonging to the first lens type, types ofdata in said fifth data corresponding to types of data included in thethird data but not included in the fourth data, and a processing meansfor carrying out a process based on the third data when thediscriminating means judges the attached lens belongs to the second lenstype and carrying out a process based on the fourth and fifth data whenthe discriminating means judges the attached lens belongs to the firstlens type.
 2. A camera system as claimed in claim 1, wherein the datawith respect to the characteristic of said lens is data relating to afocus detection and the processing means is a focus detecting means. 3.A camera system as claimed in claim 2, wherein the focus detecting meansdetects a focus condition of a plurality of focus detection areas andwherein the data with respect to the characteristic of said lensindicates which of the focus detection areas is able to be used in thefocus detection.
 4. A camera system as claimed in claim 3, wherein thedata with respect to the characteristic of said lens further indicates adifferent amount between a position of an actual focal plane and aposition to be detected in the focus detecting means.
 5. A camera systemas claimed in claim 3, wherein the data with respect to thecharacteristic of said lens further indicates a correction amount ofaberration with rays used in the focus detecting means.
 6. A camerasystem as claimed in claim 1, wherein the data with respect to thecharacteristic of said lens relates to a measurement of light.
 7. Acamera system as claimed in claim 6, wherein the data with respect tothe characteristic of said lens indicates a correction amount of themeasurement of light in condition under a fully open aperture.
 8. Acamera system having a camera body and a first and second lensesexchangeable to said camera body, comprising:said first lens comprisingmeans for outputting first data which indicates said first lens belongsto a first lens type and fourth data depending on the characteristic ofsaid first lens; said second lens comprising means for outputting seconddata which indicates said second lens belongs to a second lens type andthird data depending on the characteristic of said second lens, types ofdata in said third data including all types of data in said fourth data;said camera body comprising: means for inputting the data from theoutputting means of said first or second lens attached to said camerabody, a first storing means for storing data, a second storing means forstoring data, a third storing means for storing fifth data depending onthe characteristic of the lens belonging to the first lens type, typesof data in said fifth data corresponding to types of data included inthe third data but not included in the fourth data, means for storingthe inputted first and second data in the first storing means, means fordiscriminating the lens type based on whether the stored data is thefirst or second data, and means for storing the inputted third data inthe second storing means when the discriminating means judges theattached lens belongs to the second lens type and storing the fifth datastored in the third storing means in the second storing means when thediscriminating means judges the attached lens belongs to the first lenstype.
 9. A camera system as claimed in claim 8, wherein the stored datain the second storing means is data relating to a focus detection.
 10. Acamera system as claimed in claim 9, wherein said camera body furthercomprises means for detecting a focus condition based on the stored datain the second storing means.
 11. A camera system having a camera bodycapable of detecting each focus condition with respect to a plurality offocus detection areas, and a first and second lenses exchangeable tosaid camera body, comprising:first means, provided in said first lens,for outputting data indicating which of the focus detection areas isable to be used in the focus detection by using light rays passedthrough said first lens; second means, provided in said camera body, forjudging whether a mounted lens is the first lens or the second lens;third means, provided in said camera body, for storing data indicatingwhich of the focus detection areas is able to be used in the focusdetection by using light rays passed through said second lens; fourthmeans, provided in said camera body, for deciding which of the focusdetection areas is able to be used in the focus detection on the basisof the output results of the first means when the mounted lens is thefirst lens and on the basis of the output results of the third meanswhen the mounted lens is the second lens; and fifth means, provided insaid camera body, for calculating defocus amount with respect to thefocus detection areas decided by the fourth means.
 12. A camera systemhaving a camera body and first and second lenses exchangeable to saidcamera body, comprising:first means, provided in said camera body, fordetecting each focus condition with respect to an axial focus detectionarea and an off-axial focus detection area by using light rays passedthrough said lens; second means, provided in said first lens, foroutputting first data indicating deviation between a film plane and thefocus position based on the focus condition detected by the first meanswith respect to the axial focus detection area and outputting seconddata indicating deviation between the film plane and the focus positionbased on the focus condition detected by the first means with respect tothe off-axial focus detection area; third means, provided in said secondlens, for outputting third data indicating deviation between the filmplane and the focus position based on the focus condition detected bythe first means with respect to the axial focus detection area; fourthmeans, provided in said camera body for judging whether a mounted lensis the first lens or the second lens; fifth means, provided in saidcamera body, for outputting fifth data indicating deviation between thefilm plane and the focus position based on the focus condition detectedby the first means with respect to the off-axial focus detection areawhen the first means detects the focus condition by using light rayspassed through said second lens; and sixth means, provided in saidcamera body, for calculating defocus amount on the basis of the outputresults of the second means when the mounted lens is the first lens andon the basis of the output results of the third and fifth means when themounted lens is the second lens.
 13. A camera system as claimed in claim12, wherein said deviation between the film plane and the focus positionis caused because a F-number of the lens used by the first means doesnot confirm to a fully open F-number.
 14. A camera system as claimed inclaim 12, wherein said deviation between the film plane and the focusposition is caused because a wavelength of light rays used in the firstmeans does not confirm to a wavelength of the light rays used at anexposure on a film.